linux-kernel - [PATCH 3.16 209/294] module: fix types of device tables aliases

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Message-ID: <lsq.1510009382.560515968@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Dmitry Vyukov" <dvyukov@...gle.com>,
        "Pekka Enberg" <penberg@...nel.org>,
        "Christoph Lameter" <cl@...ux.com>,
        "David Rientjes" <rientjes@...gle.com>,
        "Konstantin Khlebnikov" <koct9i@...il.com>,
        "Sasha Levin" <sasha.levin@...cle.com>,
        "Andrey Konovalov" <adech.fo@...il.com>,
        "Joonsoo Kim" <iamjoonsoo.kim@....com>,
        "Konstantin Serebryany" <kcc@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Dmitry Chernenkov" <dmitryc@...gle.com>,
        "Ingo Molnar" <mingo@...e.hu>, "Andi Kleen" <andi@...stfloor.org>,
        "Arnd Bergmann" <arnd@...db.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Yuri Gribov" <tetra2005@...il.com>,
        "Andrey Ryabinin" <a.ryabinin@...sung.com>,
        "Dave Hansen" <dave.hansen@...el.com>
Subject: [PATCH 3.16 209/294] module: fix types of device tables aliases

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Ryabinin <a.ryabinin@...sung.com>

commit 6301939d97d079f0d3dbe71e750f4daf5d39fc33 upstream.

MODULE_DEVICE_TABLE() macro used to create aliases to device tables.
Normally alias should have the same type as aliased symbol.

Device tables are arrays, so they have 'struct type##_device_id[x]'
types. Alias created by MODULE_DEVICE_TABLE() will have non-array type -
	'struct type##_device_id'.

This inconsistency confuses compiler, it could make a wrong assumption
about variable's size which leads KASan to produce a false positive report
about out of bounds access.

For every global variable compiler calls __asan_register_globals() passing
information about global variable (address, size, size with redzone, name
...) __asan_register_globals() poison symbols redzone to detect possible
out of bounds accesses.

When symbol has an alias __asan_register_globals() will be called as for
symbol so for alias.  Compiler determines size of variable by size of
variable's type.  Alias and symbol have the same address, so if alias have
the wrong size part of memory that actually belongs to the symbol could be
poisoned as redzone of alias symbol.

By fixing type of alias symbol we will fix size of it, so
__asan_register_globals() will not poison valid memory.

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Konstantin Serebryany <kcc@...gle.com>
Cc: Dmitry Chernenkov <dmitryc@...gle.com>
Signed-off-by: Andrey Konovalov <adech.fo@...il.com>
Cc: Yuri Gribov <tetra2005@...il.com>
Cc: Konstantin Khlebnikov <koct9i@...il.com>
Cc: Sasha Levin <sasha.levin@...cle.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/module.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -135,7 +135,7 @@ void trim_init_extable(struct module *m)
 #ifdef MODULE
 /* Creates an alias so file2alias.c can find device table. */
 #define MODULE_DEVICE_TABLE(type, name)					\
-  extern const struct type##_device_id __mod_##type##__##name##_device_table \
+extern const typeof(name) __mod_##type##__##name##_device_table		\
   __attribute__ ((unused, alias(__stringify(name))))
 #else  /* !MODULE */
 #define MODULE_DEVICE_TABLE(type, name)